Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Inventory)(Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Public Utilities, Inventory [Line Items]
Materials and supplies	$ 2,389	$ 2,102
Coal held for electric generation	1,114	997
Oil, gas and other fuel held for electric generation	307	360
Public Utilities, Inventory	3,810	3,459
Duke Energy Carolinas [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	785	719
Coal held for electric generation	451	362
Oil, gas and other fuel held for electric generation	40	43
Public Utilities, Inventory	1,276	1,124
Progress Energy [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	1,133	981
Coal held for electric generation	370	329
Oil, gas and other fuel held for electric generation	248	280
Public Utilities, Inventory	1,751	1,590
Duke Energy Progress [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	776	676
Coal held for electric generation	192	150
Oil, gas and other fuel held for electric generation	120	140
Public Utilities, Inventory	1,088	966
Duke Energy Florida [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	357	305
Coal held for electric generation	178	178
Oil, gas and other fuel held for electric generation	128	140
Public Utilities, Inventory	663	623
Duke Energy Ohio [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	81	67
Coal held for electric generation	16	21
Oil, gas and other fuel held for electric generation	8	9
Public Utilities, Inventory	105	97
Duke Energy Indiana [Member]
Public Utilities, Inventory [Line Items]
Materials and supplies	301	258
Coal held for electric generation	267	275
Oil, gas and other fuel held for electric generation	2	4
Public Utilities, Inventory	$ 570	$ 537